U.S. patent application number 12/419534 was filed with the patent office on 2009-07-30 for methods and apparatus for reducing power consumption in cdma communication device.
This patent application is currently assigned to Research In Motion Limited. Invention is credited to C. Nicolas Bugnariu, M. Khaledul Islam.
Application Number | 20090190513 12/419534 |
Document ID | / |
Family ID | 32595218 |
Filed Date | 2009-07-30 |
United States Patent
Application |
20090190513 |
Kind Code |
A1 |
Islam; M. Khaledul ; et
al. |
July 30, 2009 |
Methods And Apparatus For Reducing Power Consumption In CDMA
Communication Device
Abstract
Methods and apparatus for reducing power consumption of a code
division multiple access (CDMA) communication device are described.
The CDMA communication device operates in a voice call during which
voice or audio information is communicated in frames over forward
and reverse links. During voice inactivity periods of the voice
call, a transmitter of the CDMA communication device is controlled
to enter and be maintained in low power states, for stopping
transmission of lowest rate frames that would otherwise be sent
during the voice inactivity period.
Inventors: |
Islam; M. Khaledul;
(Waterloo, CA) ; Bugnariu; C. Nicolas; (Irving,
TX) |
Correspondence
Address: |
JOHN J. OSKOREP, ESQ. LLC;ONE MAGNIFICENT MILE CENTER
980 N. MICHIGAN AVE., SUITE 1400
CHICAGO
IL
60611
US
|
Assignee: |
Research In Motion Limited
Waterloo
CA
|
Family ID: |
32595218 |
Appl. No.: |
12/419534 |
Filed: |
April 7, 2009 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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|
10737511 |
Dec 16, 2003 |
7525941 |
|
|
12419534 |
|
|
|
|
60433600 |
Dec 16, 2002 |
|
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Current U.S.
Class: |
370/311 |
Current CPC
Class: |
H04W 52/0232 20130101;
Y02D 70/144 20180101; Y02D 70/1242 20180101; Y02D 70/25 20180101;
Y02D 30/70 20200801; H04W 88/02 20130101; Y02D 70/1224
20180101 |
Class at
Publication: |
370/311 |
International
Class: |
G08C 17/00 20060101
G08C017/00 |
Claims
1. A method in a code division multiple access (CDMA) communication
device comprising the acts of: operating in a voice call during
which voice or audio information is communicated in frames over
forward and reverse links; causing a transmitter to enter and be
maintained in a low power state during a voice inactivity period of
the voice call, for stopping transmission of lowest rate frames
that would otherwise be sent during the voice inactivity period;
and causing the transmitter to be exited from the low power state
for resuming transmission for the voice call.
2. The method of claim 1, wherein the act of causing the
transmitter to enter and be maintained in the low power state
causes a transmit power of the CDMA communication device to be
reduced.
3. The method of claim 1, wherein the act of causing the
transmitter to be exited from the low power state is performed in
response to identifying voice activity for the voice call.
4. The method of claim 1, further comprising: repeating the acts of
entering and exiting the low power state for additional voice
inactivity periods of the voice call.
5. The method of claim 1, wherein the act of causing the
transmitter to enter and be maintained in the low power state
comprises the further act of disabling only a portion of the
transmitter.
6. The method of claim 1, further comprising: maintaining a
receiver enabled to receive information during the voice inactivity
period while the transmitter is in the low power state.
7. The method of claim 1, further comprising: during the low power
state of the voice call: maintaining a receiver enabled to receive
information; and receiving one or more power values through the
receiver.
8. The method of claim 1, wherein the CDMA communication device
operates in accordance with a CDMA2000 standard.
9. A code division multiple access (CDMA) communication device,
comprising: a receiver; a transmitter which includes a power
amplifier (PA); a processor coupled to the receiver and the
transmitter; the processor being adapted to: operate the receiver
and the transmitter in a voice call during which voice or audio
information is communicated in frames over forward and reverse
links; cause the transmitter to enter and be maintained in a low
power state during a voice inactivity period of the voice call, for
stopping transmission of lowest rate frames that would otherwise be
sent via the transmitter during the voice inactivity period; and
cause the transmitter to be exited from the low power state for
resuming transmission for the voice call.
10. The CDMA communication device of claim 9, wherein the processor
is further operative to reduce a transmit power of the CDMA
communication device by causing the transmitter to enter and be
maintained in the low power state.
11. The CDMA communication device of claim 9, wherein the processor
is further operative to cause the transmitter to be exited from the
low power state in response to identifying voice activity for the
voice call.
12. The CDMA communication device of claim 9, wherein the processor
is further operative to cause the transmitter to enter and be
maintained in the low power state by disabling at least a portion
of the transmitter.
13. The CDMA communication device of claim 9, wherein the processor
is further operative to cause the transmitter to enter and be
maintained in the low power state by disabling only a portion of
the transmitter.
14. The CDMA communication device of claim 9, wherein the processor
is further operative to repeat the entering and exiting of the low
power state during additional voice inactivity periods of the voice
call.
15. The CDMA communication device of claim 9, wherein the processor
is further operative to maintain the receiver enabled to receive
information while the transmitter is in the low power state.
16. The CDMA communication device of claim 9, wherein the processor
is further operative to, while the transmitter is in the low power
state, maintain the receiver enabled to receive one or more power
values during the voice call.
17. The CDMA communication device of claim 9, wherein the CDMA
communication device operates in accordance with a CDMA2000
standard.
18. A code division multiple access (CDMA) communication system,
comprising: a base station adapted to communicate in accordance
with CDMA communications; a portable electronic device adapted to
communicate with the base station in accordance with CDMA
communications; the portable electronic device being adapted to
operate in a voice call during which voice or audio information is
communicated in frames over forward and reverse links with the base
station; the portable electronic device being further adapted to,
in response to identifying that there is no voice activity at the
portable electronic device during the voice call: cause a
transmitter to enter and be maintained in a low power state during
a voice inactivity period of the voice call, for stopping
transmission of lowest rate frames that would otherwise be sent
from the portable electronic device during the voice inactivity
period; and the portable electronic device being further operative
to cause the transmitter to be exited from the low power state for
resuming transmission for the voice call.
19. The CDMA communication system of claim 18, wherein the portable
electronic device is further operative to cause the transmitter to
be exited from the low power state in response to identifying voice
activity for the voice call.
20. The CDMA communication system of claim 18, wherein the portable
electronic device is further operative to maintain a receiver of
the portable electronic device enabled to receive information while
the transmitter is in the low power state.
21. The CDMA communication system of claim 18, wherein the portable
electronic device is further operative to maintain a receiver of
the portable electronic device enabled to receive one or more power
values during the voice call while the transmitter is in the low
power state.
22. The CDMA communication system of claim 18, adapted for
communications in accordance with a CDMA2000 standard.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] The present application is a continuation of U.S.
non-provisional patent application having application Ser. No.
10/737,511 and filing date of 16 Dec. 2003, now U.S. Pat. No.
______, which claims priority to U.S. provisional patent
application having application No. 60/433,600 and filing date of 16
Dec. 2002, each application being hereby incorporated by reference
herein.
BACKGROUND
[0002] 1. Technical Field
[0003] This application relates generally to Code Division Multiple
Access (CDMA) communication techniques, and more particularly to
methods and apparatus for reducing power consumption in a CDMA
communication device which utilizes "bursty" communication
techniques.
[0004] 2. Description of the Related Art
[0005] Wideband Code Division Multiple Access (WCDMA), CDMA2000,
and Interim Standard (IS) 95 are respectively third generation
(3G), two-and-a-half generation (2.5G), and second generation (2G)
public land mobile telecommunication systems that use CDMA
communication techniques. Various standardization bodies set and
publish such standards for CDMA communication, each in their
respective areas of competence. For instance, the Third Generation
Partnership Project 2 (3GPP2) sets and publishes communication
standards for CDMA2000. Within the scope of a particular
standardization body, specific partners set and publish standards
in their respective areas.
[0006] Known CDMA communication techniques require that a mobile
station (MS) simultaneously transmit and receive signals over a
traffic channel during a communication session with a base station
(BS). Such requirements are undesirable from the standpoint of
power consumption, especially for "bursty" communications where
data or other signals may be communicated in a somewhat
discontinuous and/or sporadic fashion. Minimizing power consumption
is a relatively important objective for MSs, especially when they
are battery-powered and equipped with a relatively small battery
source.
[0007] When there is communication inactivity during a session
(e.g. no data packets or voice signals to transmit), the MS is
still required to transmit frames of lowest agreed upon rate to
maintain the session. For a data session, if a predetermined amount
of time (such as twenty seconds) elapses with no communication
activity between the BS and the MS, the session may be terminated
by the BS. In one particular technique, a CDMA MS is required to
transmit RLP idle frames at the lowest rate when the MS has no RLP
data or RLP control frames to send during an active packet data
session. Similarly, the MS is required to send the lowest rate
frames during a voice call when there is no voice, audio, or
signalling activity. As apparent, the MS and the network may
undesirably spend a significant percentage of the overall session
in "overhead" or "maintenance" in the exchange of idle frames. In
addition, if a MS and BS agree to use coherent communication on the
reverse link, this may require that the MS send a pilot channel
during a voice call or packet data session regardless of the rate
of the traffic channel. The reverse pilot channel also includes
fast forward power control channel which is used by the BS to
adjust its transmit power. Since the power of the reverse pilot
channel is relatively high in comparison to the lowest rate reverse
traffic channel, the MS may consume a significant amount of power
just by keeping its transmitter on when there is no data to
send.
[0008] Accordingly, there is a resulting need for reducing power
consumption in a CDMA communication device.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] Embodiments of the present application will now be
described, by way of example only, with reference to the attached
figures wherein the same reference numerals in different figures
are used to denote similar or the same elements:
[0010] FIG. 1 is a block diagram illustrating one example of a Code
Division Multiple Access (CDMA) network;
[0011] FIG. 2 is a block diagram illustrating a mobile station (MS)
that can be configured to act as the MS of FIG. 1 and include
preferred embodiments of the apparatus and method of the present
application;
[0012] FIG. 3 is a block diagram illustrating a protocol stack
having a preferred embodiment which employs techniques of the
present application;
[0013] FIG. 4 is a state diagram illustrating a preferred
embodiment which can co-operate with the apparatus of FIG. 3;
[0014] FIG. 5 is a graph illustrating a current consumption in an
MS during an MS-initiated communication session in which techniques
of the present application are enabled;
[0015] FIG. 6 is a graph illustrating exemplary current consumption
in an MS during an MS-initiated data call in which techniques of
the present application have been optionally disabled;
[0016] FIG. 7 is a graph illustrating exemplary current consumption
at an MS during a BS-initiated data call in which techniques of the
present application are enabled;
[0017] FIG. 8 is a graph illustrating exemplary current consumption
at an MS during a BS-initiated data call in which techniques of the
present application have been optionally disabled; and
[0018] FIGS. 9A and 9B are graphs illustrating exemplary power
variation and rate variation of the TX Radio Link Protocol (RLP) at
a MS during an MS-initiated data call in which techniques of the
present application have been enabled.
DETAILED DESCRIPTION OF THE DRAWINGS
[0019] Methods and apparatus for reducing power consumption in a
code division multiple access (CDMA) communication device are
described herein. The CDMA device may be a battery-powered mobile
station (MS) or, alternatively, a base station (BS). The CDMA
communication device is configured to wirelessly communicate based
on an IS-95, an IS-2000, a CDMA2000, or other similar or related
standard.
[0020] The CDMA device is configured to operate in a communication
session (e.g. a data-packet or a voice call session) during which
information is communicated over an information channel. Examples
of such information include user data, signalling information from
the MS such as a hand-off request message, and forward link power
control information to adjust the power of the BS. At some time
during this session, the device identifies that there is no
information to transmit from its transmitter. In response, the
device places its transmitter into a low power state during at
least a portion of the session. Preferably, a modulator and a power
amplifier (PA) of the transmitter are shut off in the low power
state. Alternatively, for example, a power setting of the PA may be
set to a zero or other negligible value in the low power state.
[0021] During the low power state, the device refrains from
transmitting any information (e.g. including Radio Link Protocol
(RLP) idle frames) which would otherwise normally be transmitted.
However, the CDMA device may maintain operation of its receiver to
receive information while the transmitter is in the low power
state. In particular, during the low power state the CDMA device
may monitor the variation of the BS power through its receiver and
store transmitter power values which are based on these received
values. The CDMA device may cause its transmitter to exit the low
power state before an expiration of a fade timer, to thereby
imitate a brief "fade" in the communication system.
[0022] The details of such methods and apparatus disclosed herein
enable mobile stations to communicate with base stations using
bursty CDMA techniques which do not require that the MS transmitter
remain on throughout the exchange with the BS. It is a particular
object of the present application that the methods and apparatus of
"bursty" CDMA communication are provided at a MS to enable it to
make intelligent decisions as to when it can turn off the
transmitter to take advantage of data/voice inactivity in a stable
RF environment, how long it can keep the transmitter off without
dropping the communication session, and operating in such a manner
so as to maintain compliance with the applicable CDMA standard.
[0023] Advantageously, the techniques of the present application
can be adapted to co-operate with known CDMA standards by operating
to simulate or imitate a MS "fade" as seen by the BS. In a typical
CDMA-compliant embodiment, a BS which follows a CDMA standard will
typically assume that the MS has faded if the BS has not received
any valid data from MS. If fading lasts for more than a
predetermined amount of time, such as five (5) seconds, the BS will
terminate the session (e.g. release the call) in response to such
time expiration. If the MS intentionally decides not to transmit
during certain intervals (i.e. it does not transmit otherwise
required RLP idle frames) but still meets the fade timeout
criteria, these intervals will appear to the BS as if the MS is
merely undergoing a fade where all rake fingers of the BS's CDMA
receiver are out of lock. In such conditions, a typical BS
implementation does not increase its transmit power but begins
sending alternate UP-DOWN (or a fixed pattern) commands every
forward link frame to the MS for reverse link transmit power.
Advantageously, this embodiment merely requires that lower layers
of the CDMA protocol stack be modified to reap the benefits of
lower power consumption.
[0024] In a particular embodiment, which is implemented in a MS
physical layer of the CDMA protocol stack, three (3) major states
are associated with controlling the power amplifier of the
transmitter: PA_ON_SLOW, PA_OFF, and PA_ON_REGULAR. The transmitter
is switched to and remains in the PA_ON_REGULAR state when data is
being sent. However, the transmitter is switched to the PA_ON_SLOW
state in a stable radio environment when the MS starts sending RLP
idle frames during data inactivity, or lowest rate frames during
voice call inactivity along with fast forward power control, if
applicable. The term "stable radio environment" is used herein to
indicate the condition when the MS decides that there is no need to
adjust the forward link information channel power of the BS. In the
PA_ON_SLOW state, the MS starts to transmit information and makes
necessary preparation to enter the PA_OFF state where the power
amplifier (PA) of the transmitter can be shut off. As soon as power
control loop stability is reached, the transmitter is switched to
the PA_OFF state.
[0025] Different techniques may be utilized in making this
transition. In a first method, a timer is utilized, the expiration
of which triggers the state transition. Alternatively, a second
method takes advantage of a typical base station implementation
which sends alternate UP-DOWN (or fixed pattern) commands during
the time the MS is perceived to be undergoing a fade. If the BS
supports this implementation, then the MS switches to the PA_OFF
state when it detects on a consistent basis that the BS is no
longer sending equal UP-DOWN (or fixed pattern) commands. This
serves as an indication that the BS has reacquired the MS and
started regular adjustment of reverse link power. Once this
condition is detected, the MS waits for a small period of time that
is required for stability. This second method is preferred over the
first one, as it is adaptive and optimizes the duration of
PA_ON_SLOW state.
[0026] In the PA_OFF state, the transmitter's PA is turned off;
however, the receiver remains on. This effectively conserves power
at the MS and at the same time conserves spectrum (i.e. there is
less interference in the reverse link). To ensure backwards
compatibility, in one embodiment the transmitter remains in the
PA_OFF state for a certain period of time that satisfies the fading
timeout criteria. Then, the state is changed back to the PA_ON_SLOW
state. At any moment if there is any non-idle frame that needs to
be sent out (such as new data or control frame, voice, signalling
message, forward power control), the device automatically switches
to the PA_ON_REGULAR state.
[0027] Other aspects and features of the present application will
become apparent to those ordinarily skilled in the art upon review
of the following description of specific embodiments.
[0028] As described herein, a method of reducing power consumption
in a code division multiple access (CDMA) communication device
includes the acts of operating the device in a communication
session during which information is communicated over an
information channel; identifying that there is no information to
transmit by the CDMA communication device; and during at least a
portion of the communication session, causing a transmitter of the
CDMA communication device to be maintained in a low power state
based at least in part on the act of identifying. In the low power
state, the transmitter does not transmit any information that it
would normally be accustomed to transmit. The term "information" is
used herein to broadly indicate all forms of data that the MS
transmits, such as user data, signalling information such as a
hand-off request message, forward link power control information to
adjust the power of the BS, and Radio Link Protocol (RLP) idle
frames, etc. The low power state is preferably maintained for a
duration of time that is less than a fade timer expiration.
[0029] A CDMA communication device of the present application
(which may be a mobile station or a base station) is configured to
wirelessly communicate based on an IS-95, an 15-2000, a CDMA2000,
or other similar or related standard. The CDMA device includes a
receiver; a transmitter which includes a power amplifier (PA); an
antenna coupled to the receiver and the transmitter; and a
processor coupled to the receiver and the transmitter. The
processor operates the CDMA communication device in a communication
session during which information is communicated over an
information channel, identifies that there is no information to
transmit and, during at least a portion of the communication
session, causes the transmitter to enter into a low power state
based at least in part on no information being required to transmit
over the information channel. Again, the transmitter does not
transmit any information that it would normally be accustomed to
transmit during this low power state. The low power state is
preferably maintained for a duration of time that is less than a
fade timer expiration.
[0030] A CDMA communication system of the present application
includes a base station operative for CDMA communication and a
portable electronic device operative for CDMA communication with
the base station. The portable electronic device is configured to
operate in a communication session during which information is
communicated with the base station over an information channel, to
identify during the communication session that there is no
information to transmit to the base station; and to cause a
transmitter of the portable electronic device to enter into a low
power state based at least in part on no information being
available to transmit. Again, the portable electronic device does
not transmit any information that it would normally be accustomed
to transmit during this low power state. The low power state is
preferably maintained for a duration of time that is less than a
fade timer expiration.
[0031] In other variations, a method of reducing power consumption
in a battery-operated mobile station which operates in accordance
with a code division multiple access (CDMA) technique includes the
acts of operating in a communication session during which
information is communicated with a serving base station over an
information channel; based on identifying that there is no
information to transmit, powering down a transmitter power
amplifier (PA) during a portion of the communication session such
that no signals are transmitted to the serving base station; and
powering up the transmitter PA before an expiration of a fade timer
of the serving base station. A battery-powered CDMA mobile station
of the present application includes a CDMA receiver; a CDMA
transmitter; a processor coupled to the CDMA receiver and the
transmitter. The processor operates the CDMA receiver and
transmitter in a communication session during which information is
communicated over an information channel, shuts down a power
amplifier (PA) of the CDMA transmitter during a portion of the
communication session based on identifying that there is no
information to transmit; and powers up the PA before an expiration
of a fade timer of a serving base station. While the PA is shut
down, the CDMA transmitter does not transmit any information that
it would normally be accustomed to transmit.
[0032] Referring to the drawings, FIG. 1 is a block diagram
illustrating one example of a Code Division Multiple Access (CDMA)
network 100. A mobile station (MS) 102 is shown "visiting" an
access provider network 104 outside of its home network. Access
provider network 104 includes a radio network (RN) 106, a Packet
Data Service Node (PDSN) 108, a Remote Authentication Dial-In User
Service (RADIUS) server 110, and a Mobile Switching Center (MSC)
112. MS 102 is shown as associated with an RN 114 and PDSN 116
("target" structure), which are similar in structure and
functionality to RN 106 and PDSN 108, respectively ("serving"
structure). The RN is the infrastructure for connecting wireless
base stations (BSs) to MSs and onto data networks. Within an RN,
multiple BSs are included (although not expressly shown). A PDSN,
such as PDSN 108, is a wireless-aware router that acts as an
interface to the Internet (e.g. through an IP network 118) and the
RN to transport packets to and from MS 102. RADIUS server 110 is
used for authentication, authorization, and accounting purposes.
MSC 112 enables voice and other circuit-switched communications,
such as Short Message Service (SMS), being communicative through an
SS7 network 120. Other conventional components and connections
shown are either part of the core network, visiting networks, or
the home network. For example, MSC 112 is coupled to a Home
Location Register (HLR) of a home access provider network 122; a
RADIUS server of a home IP network 124 is coupled to IP network
118; a RADIUS server of a broker network 126 is coupled to IP
network 118; and a home agent (HA) of a home IP network 128 (or
other) is coupled to IP network 118.
[0033] Operationally, when MS 102 powers up, it sends a
registration message to RN 114 which validates registration with an
HLR and assigns MS 102 to a Visitor Location Register (VLR) (not
shown) if necessary. An Internet-Protocol (IP)-connected MS 102
sends a request to RN 114 to setup a Point-to-Point Protocol (PPP)
session in order to get either an IP address in a "simple" IP
network, a Care-Of Address (COA) in a mobile IP network, or other
equivalent IP-type address of another IP network. Once the radio
link protocol is established between MS 102 and RN 114, RN 114
initiates an R-P interface between RN 114 and PDSN 116. MS 102 is
authenticated by a serving PDSN 108 via RADIUS server 110 and
subsequently assigned an IP address. PDSN 116 then provides MS 102
with connectivity to, as examples, the Internet, an intranet, or
more generally an IP network.
[0034] Turning now to FIG. 2, FIG. 2 is a block diagram
illustrating a mobile station (MS) 200 that can be configured to
both act as MS 102 of FIG. 1 and include preferred embodiments of
the apparatus and method of the present application. MS 200 is
preferably a two-way wireless communication device having at least
voice and data communication capabilities. MS 200 preferably has
the capability to communicate with other computer systems on the
Internet. Depending on the exact functionality provided, this
wireless device may be referred to as a data messaging device, a
two-way pager, a wireless e-mail device, a cellular telephone with
data messaging capabilities, a wireless Internet appliance, or a
data communication device, as examples.
[0035] Where MS 200 is enabled for two-way communication through a
communication network 219, it will incorporate a communication
subsystem 211, including both a receiver 212 and a transmitter 214,
as well as associated components such as one or more, preferably
embedded or internal, antenna elements 216 and 218, local
oscillators (LOs) 213, and a processing module such as a digital
signal processor (DSP) 220. As will be apparent to those skilled in
the field of communications, the particular design of the
communication subsystem 211 will be dependent upon the
communication network in which the device is intended to operate.
For example, MS 200 may include a communication subsystem 211
designed to operate within the Mobitex.TM. mobile communication
system, the DataTAC.TM.mobile communication system, a General
Packet Radio Service (GPRS) network, Universal Mobile
Telecommunications System (UMTS) network, Enhanced Data rates for
GSM Evolution (EDGE) network, or other CDMA network.
[0036] Network access requirements will also vary depending upon
the type of network 219. In Mobitex and DataTAC networks, for
example, MS 200 is registered on network 219 using a unique
identification number associated with each MS. In UMTS and GPRS
networks, however, network access is associated with a subscriber
or user of MS 200. A GPRS MS therefore requires a subscriber
identity module (SIM) card in order to operate on a GPRS network.
Without a valid SIM card, a GPRS MS will not be fully functional.
Local or non-network communication functions, as well as legally
required functions (if any) such as "911" emergency calling, may be
available, but MS 200 will be unable to carry out any other
functions involving communications over the network 219. A SIM
interface 244 is normally similar to a card-slot into which a SIM
card can be inserted and ejected like a diskette or PCMCIA card.
The SIM card may have approximately 64K of memory and hold many key
configuration 251, and other information 253 such as
identification, and subscriber related information.
[0037] When required network registration or activation procedures
have been completed, MS 200 may send and receive communication
signals over network 219. Signals received by antenna 216 through
network 219 are input to receiver 212, which may perform such
common receiver functions as signal amplification, frequency down
conversion, filtering, channel selection and the like, and in the
example system shown in FIG. 2, analog-to-digital (A/D) conversion.
A/D conversion of a received signal allows more complex
communication functions such as demodulation and decoding to be
performed in DSP 220. In a similar manner, signals to be
transmitted are processed, including modulation and encoding, for
example, by DSP 220 and input to transmitter 214 for
digital-to-analog (D/A) conversion, frequency up conversion,
filtering, amplification and transmission over network 219 via
antenna 218. DSP 220 not only processes communication signals, but
also provides for receiver and transmitter control. For example,
the gains applied to communication signals in receiver 212 and
transmitter 214 may be adaptively controlled through automatic gain
control algorithms implemented in DSP 220.
[0038] MS 200 preferably includes a microprocessor 238 which
controls the overall operation of the device. Communication
functions, including at least data and voice communications, are
performed through communication subsystem 211. Microprocessor 238
also interacts with further device subsystems such as a display
222, a flash memory 224, a random access memory (RAM) 226,
auxiliary input/output (I/O) subsystems 228, a serial port 230, a
keyboard 232, a speaker 234, a microphone 236, a short-range
communications subsystem 240, and any other device subsystems
generally designated as 242. Some of the subsystems shown in FIG. 2
perform communication-related functions, whereas other subsystems
may provide "resident" or on-device functions. Notably, some
subsystems, such as keyboard 232 and display 222, for example, may
be used for both communication-related functions, such as entering
a text message for transmission over a communication network, and
device-resident functions such as a calculator or task list.
[0039] Operating system software used by the microprocessor 238 is
preferably stored in a persistent store such as flash memory 224,
which may alternatively be a read-only memory (ROM) or similar
storage element (not shown). Those skilled in the art will
appreciate that the operating system, specific device applications,
or parts thereof, may be temporarily loaded into a volatile memory
such as RAM 226. Received communication signals may also be stored
in RAM 226.
[0040] As shown, flash memory 224 can be segregated into different
areas for both computer programs 258 and program data storage 250,
252, 254 and 256. These different storage types indicate that each
program can allocate a portion of flash memory 224 for their own
data storage requirements. Microprocessor 238, in addition to its
operating system functions, preferably enables execution of
software applications on the MS 200. A predetermined set of
applications that control basic operations, including at least data
and voice communication applications for example, will normally be
installed on MS 200 during manufacturing. A preferred software
application may be a personal information manager (PIM) application
having the ability to organize and manage data items relating to
the user of the MS 200 such as, but not limited to, e-mail,
calendar events, voice mails, appointments, and task items.
Naturally, one or more memory stores would be available on MS 200
to facilitate storage of PIM data items. Such PIM application would
preferably have the ability to send and receive data items, via the
wireless network 219. In a preferred embodiment, the PIM data items
are seamlessly integrated, synchronized and updated, via network
219, with MS 200 user's corresponding data items stored or
associated with a host computer system. Further applications may
also be loaded onto MS 200 through network 219, auxiliary I/O
subsystem 228, serial port 230, short-range communications
subsystem 240, or other suitable subsystem 242, and installed by a
user in RAM 226 or preferably a non-volatile store (not shown) for
execution by microprocessor 238. Such flexibility in application
installation increases the functionality of the device and may
provide enhanced on-device functions, communication-related
functions, or both. For example, secure communication applications
may enable electronic commerce functions and other such financial
transactions to be performed using MS 200.
[0041] In a data communication mode, a received signal such as a
text message or web page download will be processed by the
communication subsystem 211 and input to the microprocessor 238,
which preferably further processes the received signal for output
to display 222, or alternatively to auxiliary I/O device 228. A
user of MS 200 may also compose data items such as email messages,
for example, using keyboard 232, which is preferably a complete
alphanumeric keyboard or telephone-type keypad, in conjunction with
display 222 and possibly auxiliary I/O device 228. Such composed
items may then be transmitted over a communication network through
communication subsystem 211. For voice communications, overall
operation of MS 200 is similar, except that received signals would
preferably be output to speaker 234 and signals for transmission
would be generated by microphone 236. Alternative voice or audio
I/O subsystems, such as a voice message recording subsystem, may
also be implemented on MS 200. Although voice or audio signal
output is preferably accomplished primarily through speaker 234,
display 222 may also be used to provide an indication of the
identity of a calling party, the duration of a voice call, or other
voice call related information, for example.
[0042] Serial port 230 in FIG. 2 would normally be implemented in a
personal digital assistant (PDA)-type MS for which synchronization
with a user's desktop computer (not shown) may be desirable, but is
an optional device component. Such a port 230 would enable a user
to set preferences through an external device or software
application and would extend the capabilities of MS 200 by
providing for information or software downloads to MS 200 other
than through a wireless communication network. The alternate
download path may for example be used to load an encryption key
onto the device through a direct and thus reliable and trusted
connection to thereby enable secure device communication. Other
communications subsystems 240, such as a short-range communications
subsystem, is a further optional component which may provide for
communication between MS 200 and different systems or devices,
which need not necessarily be similar devices. For example,
subsystem 240 may include an infrared device and associated
circuits and components or a Bluetooth.TM. communication module to
provide for communication with similarly enabled systems and
devices.
[0043] When MS 200 is used as MS 120 of FIG. 1, protocol stacks 246
and transceiver 211 cooperate to perform more specific techniques
of the present application. Protocol stacks 246 are shown connected
to both microprocessor 238 and DSP 220 of transceiver 211, so that
the higher layer protocols can be handled by microprocessor 238
whereas the lower layers protocols can be handled by DSP 220. One
protocol stack which can be included in block 246 is described
below in FIG. 3. Furthermore, the method of FIG. 4 can be carried
out by DSP 220 and/or microprocessor 238.
[0044] FIG. 3 is a block diagram illustrating a protocol stack 300
in a preferred embodiment of the present application. Protocol
stack 300 of FIG. 3 is illustrated as having an apparatus in a
physical layer 320 for monitoring physical layer activity with use
of a transmit/receive/forward power control (TX/RX/FPC) activity
monitor 327. TX/RX/FPC activity monitor 327 is operative to detect
activity (or lack thereof) at physical layer 320 and, based on that
activity (or lack thereof), controlling a transmitter 314 using a
TX/RX activity-based TX controller 325. TX/RX activity (or lack
thereof) can be caused by the higher layers, illustrated by Open
Systems Interconnection (OSI) Layers 2-7, or could be caused by
transmitter 314 and receiver 316 below OSI Layer 1 (i.e. physical
layer 320). In addition, TX/RX/FPC activity monitor 327 detects the
change in forward link radio conditions and decides when an
adjustment is necessary. This can be done via monitoring different
metrics associated with the forward link quality. Examples of such
metrics include total received power, forward link information
channel power, frame error rate, forward power control decisions
that would have been sent if the transmitter was on, etc. Other
components of FIG. 3 are well known.
[0045] TX/RX/FPC activity-based TX controller 325 is coupled to
TX/RX/FPC activity monitor 327 so that, when the latter detects
activity (or lack thereof) the former can control transmitter 314
based on the activity (or lack thereof). Of particular interest is
its control of a power amplifier (PA) 315 of transmitter 314, which
may involve ON/OFF control thereof (i.e. whether PA 315 amplifies
and emits a radio signal or not) and/or control over the transmit
power rate of change (i.e. how quickly PA 315 responds to power
control commands, such as UP/DOWN commands, issued by the BS).
Thus, it is possible to selectively control transmitter 314 so
that, during periods of inactivity, transmitter 314 can be turned
off. For example, transmitter 314 may be turned off during data
inactivity in a data packet session in a stable radio environment
when Radio Link Protocol (RLP) idle frames and/or fast forward
power control would otherwise be normally sent. As another example,
transmitter 314 may be turned off during a silent period in a voice
call in a stable radio environment when lowest rate frames would
otherwise normally be sent. When activity is identified,
transmitter 314 is turned back on. It is preferred to operate the
apparatus of FIG. 3 in such a manner that it co-operates with
existing BSs, particularly by controlling transmitter 314 in a way
which simulates or imitates fading, as will be further described
further in reference to FIG. 4.
[0046] By turning off transmitter 314, it is placed into a low
power state. Alternatively, programmable circuits in transmitter
314 may be disabled, or set to zero or other negligible value to
maintain a low power state. In the low power state, all or only
portions of transmitter 314 may be disabled or shut down.
[0047] FIG. 4 is a state diagram illustrating the preferred
embodiment of the present communication method which may cooperate
with the apparatus of FIG. 3. In FIG. 4, a state machine 400 having
three main states is shown: a PA_ON_SLOW state 420, a PA_OFF state
430, and a PA_ON_REGULAR state 410. The names of the states are a
juxtaposition of the ON/OFF state of the PA (PA_ON and PA_OFF) and
the rate of change of the transmit power in response to power
control commands from the BS (REGULAR and SLOW).
[0048] In PA_ON_REGULAR 410 state, the PA is maintained powered ON
as is conventional and the step size of the correction factor for
the MS transmit power is changed at a regular rate (e.g. using a
step size which corresponds to what is requested by the BS, such as
a 1 dB step size). In state 410, the MS transmitter power value is
given by: TX=(RX+constant+regular correction). Also, in state 410
the transmitter functions as a conventional transmitter until a
transmit inactivity threshold is exceed, upon the occurrence of
which the state changes to PA_ON_SLOW 420 state. An exemplary
inactivity threshold is that of receiving a single RLP idle frame.
If the MS sends any signalling message, then it keeps the
transmitter ON for a certain period of time. This is necessary for
a variety of reasons, such as for a handoff scenario. In case of a
handoff, the handoff request needs to be granted by the BS and the
handoff process needs to be completed, which requires that the MS
is acquired by the target BS.
[0049] In PA_ON_SLOW state 420, the PA is maintained powered ON as
was the case in the PA_ON_REGULAR state 410. However, the step size
of the correction factor for the MS transmit power is changed at a
slower rate (i.e. using a step size which is a scaled down value of
what is requested by the BS; for example, using a quarter scale
results in a 0.25 dB step size). In state 420, the MS transmitter
power value is given by the expression TX=(RX+constant+slow
correction). Upon entering state 420, a "power save init timer" is
started (assuming method 1 is used) which has, for example, a 200
millisecond (msec) time duration. While in state 420, the
transmitter functions as a conventional transmitter until one of
two events: until the power save init timer has expired whereupon
the state changes to PA_OFF state 430 (described below); or until
there is requirement for transmit activity (e.g. due user data,
signalling, or need to send forward power control (FPC)
information) whereupon the state changes to PA_ON_REGULAR state 410
(described above).
[0050] In PA_OFF state 430, the PA and/or other transmitter
components are maintained powered OFF. However, the MS transmitter
power value may be updated based on the received BS power values,
resulting in an open loop tracking. Such power values are stored in
memory as is conventional. In state 430, the MS transmitter power
value is given by the expression TX=(RX+constant). Upon entering
state 430, a "power save fading timer" is started which has, for
example, a duration which is a fraction of the fade timeout of the
BS, for instance 1/2 of 5 seconds or 21/2 seconds. While in state
430, the transmitter does not function as a conventional
transmitter in that the PA is turned off, to thereby simulate or
imitate a fade of the MS as seen by the BS. The modulator and/or
other portions of the transmitter may be powered down or disabled
as well. State 430 is maintained until either: until the power save
fading timer has expired whereupon the state changes to the
above-described PA_ON_SLOW state 420; or until there is requirement
for transmitter activity whereupon the state changes to the
above-described PA_ON REGULAR state 410.
[0051] An alternate technique may be used to transition from
PA_ON_SLOW state 420 to PA_OFF state 430. This technique takes
advantage of a typical BS implementation which sends alternate
UP-DOWN (or a fixed pattern) commands during the time the MS is
perceived to be undergoing the fade. If the BS supports this
implementation, the MS switches to PA_OFF state 430 when it detects
on a consistent basis that the BS no longer sends equal UP-DOWN (or
a fixed pattern) commands. This serves as an indication that the BS
has reacquired the MS and has started regular adjustment of the
reverse link power. Once this condition is detected, the MS waits
for a small period of time that is required for stability before
entering PA_OFF state 420.
[0052] In an alternate embodiment, only PA_ON_REGULAR and PA_OFF
states 410 and 430 are utilized and PA_ON_SLOW state 420 is
optional. In another alternative embodiment, the MS determines if
the BS is enabled to receive bursty CDMA communication from a MS
and, if so determined, the MS need not simulate fading so as to
render PA_ON_SLOW state 420 unnecessary. In yet another alternative
embodiment, the MS optionally disables or enables steps of the
technique by configuration operation, allowing a MS that is capable
of bursty CDMA communication to be also enabled for traditional
CDMA communication.
[0053] FIG. 5 is a graph 500 illustrating current consumption at an
MS during an MS-initiated communication session in which techniques
of the present application have been enabled. The MS sends a
request to set up a data session (event 510). After negotiation
between the MS and the BS, a traffic channel is set up (event 520).
During this time, the device is in the PA_ON_REGULAR state since it
is has information to send (event 530). After radio link protocol
is established, data is sent from the MS and acknowledgment is
received (event 550). Data inactivity then occurs, which in turn
forces a transition to the PA_ON_SLOW state (event 540). After
transmission of a number of idle frames, the PA is turned OFF
(event 560) since there is no TX/FPC activity. Here, the receiver
is still ON so that the MS can track the open loop transmit power
that would be required when it turns the transmitter PA on again.
When the inactivity timer expires (assuming method 1 is used), the
MS sends an indication to the BS that it desires to enter a dormant
state (event 570). This results in signalling activity, which in
turn forces a transition to the PA_ON_REGULAR state (event 580).
Once the message transmission is over, the MS re-enters the
PA_ON_SLOW state and eventually turns off the PA when it gets
acknowledgment from the network that the call can be released. The
MS starts reacquiring the system (event 590) to make sure that it
has most recent network configuration data after the call is over
and then goes into slotted sleep mode (event 595).
[0054] FIG. 6 is a graph 600 illustrating exemplary current
consumption at an MS during an MS-initiated communication session
in which the techniques of the present application have been
optionally disabled. The MS sends a request to set up a data
session (event 610). After negotiation between the MS and the BS, a
traffic channel is set up (event 620). The transmit PA is ON with
the ramp controlled by the BS based on radio frequency (RF)
conditions (event 630). After radio link protocol is established,
data is sent from the MS and acknowledgment is received (event
640).
[0055] The MS and BS start exchanging Radio Link Protocol (RLP)
idle frames during the period of data inactivity. When the
inactivity timer expires, the MS releases the data call to enter
dormant state (event 650). The MS stops the PA when it gets
acknowledgment from the network that the call can be released. The
MS starts reacquiring the system (event 660) to make sure that it
has most recent network configuration data after the call is over
and goes to slotted sleep (event 670).
[0056] FIG. 7 is a graph 700 illustrating exemplary current
consumption at an MS during a BS-initiated communication session in
which techniques of the present application have been enabled. Once
the MS has received data and has sent acknowledgement, data
inactivity begins. Since the forward link RF is stable, the MS
makes use of it by turning the PA OFF to simulate a temporary fade
(event 710). The receiver is still ON so that the MS can track the
open loop transmit power that would be required whenever it turns
the transmit PA ON again. When the power save fade timer expires
(assuming method 1 is used), the MS enters the PA_ON_SLOW state and
resumes transmission using the open loop value with slow ramp.
Since there is still no required transmit activity, the MS
transitions back to PA OFF state after some time. Transitions
between the PA_OFF and the PA_ON_SLOW states continue until the
call is released by the BS. The MS goes to the PA_ON_REGULAR state
to acknowledge the release order and enters slotted sleep mode
after reacquiring the system.
[0057] FIG. 8 is a graph 800 illustrating exemplary current
consumption at an MS during a BS-initiated data call in which
techniques of the present application have been optionally
disabled. Once the MS has received data and sent acknowledgements,
data inactivity begins. The MS and the BS start exchanging RLP idle
frames. The transmit PA is ON throughout the duration with ramp
controlled by the BS based on the RF conditions (event 810). The MS
acknowledges the release order when the BS terminates the call and
enters slotted sleep mode after reacquiring the system.
[0058] FIG. 9 is a graph 900 illustrating exemplary power variation
and rate variation of the TX RLP at an MS during an MS-initiated
communication session in which techniques of the present
application have been enabled. Similar to event 500 of FIG. 5, the
MS has received an acknowledgement that the data was received
(event 910). Data inactivity commences shortly after that (event
920). As a result, the MS transitions to the PA_OFF state with its
receiver still ON (event 930). As soon as the MS stops
transmitting, the BS initially responds by asking the MS to
increase its power. Once the BS realizes that its receiver has lost
track of the MS, it assumes that the MS is undergoing a "fade" and
starts sending alternate UP/DOWN commands (event 940). This means
that, if the MS were to listen to BS's command, the transmit power
over one frame would have been unchanged. The MS internally
maintains the would-be open loop transmit power based on received
power during the PA_OFF state. When the inactivity timer expires
(event 950), the MS enters the regular PA_ON mode and releases the
call (event 960). If the BS requires a periodic report of the
forward link quality metrics, the MS still sends this information
whenever it is time to send it. This can serve as an indication to
the BS of the quality of the forward link as measured by the
MS.
[0059] Thus, methods of reducing power consumption in a code
division multiple access (CDMA) communication device have been
described. One method includes the acts of operating the device in
a communication session during which information is communicated
over an information channel; identifying that there is no
information to transmit by the CDMA communication device; and
during at least a portion of the communication session, causing a
transmitter of the CDMA communication device to be maintained in a
low power state based at least in part on the act of identifying.
In the low power state, the transmitter does not transmit any
information (including idle frames) that it would normally be
accustomed to transmit. The low power state is maintained for a
duration of time that is less than a fade timer expiration. If
there any requirement for transmission of information prior to this
expiration, the state is terminated early and the MS enters a
normal transmit mode.
[0060] A CDMA communication device of the present application
(which may be a mobile station or a base station) includes a
receiver; a transmitter which includes a power amplifier (PA); an
antenna coupled to the receiver and the transmitter; and a
processor coupled to the receiver and the transmitter. The
processor operates the CDMA communication device in a communication
session during which information is communicated over an
information channel, identifies that there is no information to
transmit and, during at least a portion of the communication
session, causes the transmitter to enter into a low power state
based at least in part on no information being available to
transmit over the information channel. Again, the transmitter does
not transmit any information that it would normally be accustomed
to transmit during this low power state. The low power state is
preferably maintained for a duration of time that is less than a
fade timer expiration.
[0061] A CDMA communication system of the present application
includes a base station operative for CDMA communication and a
portable electronic device operative for CDMA communication with
the base station. The portable electronic device is configured to
operate in a communication session during which information is
communicated with the base station over an information channel, to
identify during the communication session that there is no
information to transmit to the base station; and to cause a
transmitter of the portable electronic device to enter into a low
power state based at least in part on no information being
available to transmit. Again, the portable electronic device does
not transmit any information that it would normally be accustomed
to transmit during this low power state. The low power state is
preferably maintained for a duration of time that is less than a
fade timer expiration.
[0062] In other variations, a method of reducing power consumption
in a battery-operated mobile station which operates in accordance
with a code division multiple access (CDMA) technique includes the
acts of operating in a communication session during which
information is communicated with a serving base station over an
information channel; based on identifying that there is no
information to transmit, powering down a transmitter power
amplifier (PA) during a portion of the communication session such
that no signals are transmitted to the serving base station; and
powering up the transmitter PA before an expiration of a fade timer
of the serving base station. A battery-powered CDMA mobile station
of the present application includes a CDMA receiver; a CDMA
transmitter; a processor coupled to the CDMA receiver and the
transmitter. The processor operates the CDMA receiver and
transmitter in a communication session during which information is
communicated over an information channel, shuts down a power
amplifier (PA) of the CDMA transmitter during a portion of the
communication session based on identifying that there is no
information to transmit; and powers up the PA before an expiration
of a fade timer of a serving base station. While the PA is shut
down, the CDMA transmitter does not transmit any information that
it would normally be accustomed to transmit.
[0063] The above-described embodiments of the present application
are intended to be examples only. Those of skill in the art may
affect alterations, modifications and variations to the particular
embodiments without departing from the scope of the
application.
* * * * *